1. Field of the Invention
The present invention relates to a circuit substrate, and more particularly to a circuit substrate having a power/ground plane with grid holes.
2. Description of the Related Art
FIG. 1 shows a top view of a conventional circuit substrate. The conventional circuit substrate 1 is a substrate for window ball grid array (WBGA) package, which comprises a window 11, a plurality of power/ground planes 12, a plurality of fingers 13, a plurality of I/O ball pads 14, a plurality of power/ground ball pads 15 and a plurality of conductive traces 16. The fingers 13 are disposed at the periphery of the window 11. Each power/ground plane 12 has a plurality of grid lines 121, and the grid lines 121 intersect each other to define a plurality of grid holes 122. The material of the power/ground planes 12 is copper, and the grid lines 121 and the grid holes 122 are formed by etching a large area made of copper. For reliability, the grid lines 121 and the grid holes 122 are evenly distributed, so as to increase air dissipation and the bonding strength between two laminated layers.
The I/O ball pads 14 are electrically connected to some of the fingers 13 by some of the conductive traces 16. The power/ground ball pads 15 are disposed on the power/ground planes 12, and the power/ground planes 12 are electrically connected to the other fingers 13 by the other conductive traces 16. The fingers 13 are electrically connected to a chip (not shown), and a plurality of solder balls (not shown) are formed on the I/O ball pads 14 and the power/ground ball pads 15.
The disadvantage of the conventional circuit substrate 1 is described as follows. Since the power/ground plane 12 is an important source of power signal and ground signal, the grid holes 122 disposed thereon will influence the resistance of power signal and ground signal, thereby reducing power integrity.
Therefore, it is necessary to provide a circuit substrate having a power/ground plane with grid holes to solve the above problem.